The present invention relates to control systems for motor vehicle subsystems, and more particularly to a system and method including a dynamic feedforward feature for integrated control of the motor vehicle steering and brakes.
Unified or integrated chassis control systems have been proposed which control the brakes, steering, and suspension of a motor vehicle. The purpose of unified chassis control is to improve vehicle performance in all driving conditions by coordinating control of the chassis subsystems. Unified chassis control systems typically utilize a supervisory control concept that utilizes three fundamental blocks: a reference model, a state estimator, and a vehicle control. The vehicle control element normally incorporates a feedback control. This element computes control values by comparing actual states obtained from the state estimator with desired states from the reference model.
It is well known that when brakes are applied during a steering maneuver, a yaw rate error is induced. It such circumstances, the conventional chassis control systems are relatively slow to compensate.
The present invention is a system and method for controlling a motor vehicle subsystem. The control system comprises a reference model and a feedforward controller. The reference model computes desired states of the subsystem. The feedforward controller computes a first control value based on input from the reference model, and computes a second control value based on yaw rate of the vehicle and a control variable for the subsystem.
Accordingly, it is an object of the present invention to provide a control system of the type described above which presents a standard methodology to integrate feedforward control into a unified chassis control supervisor that overcomes several known deficiencies.
Another object of the present invention is to provide a control system of the type described above which improves control response.
Still another object of the present invention is to provide a control system of the type described above which allows single-point tuning.
Still another object of the present invention is to provide a control system of the type described above which incorporates dynamic feedforward logic.